<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  
</head>
<body>

  <!-- html代码 -->
  <script>
    // js代码
    var a = 1 

    // a = 2

    var b = 'snail'
    var c = true
    var d = false

    var $1 = 'a'
    var _1 = 'a'

    var goodsname = '商品名称'


    // 这个a被我们称为变量，内部会存储数据。
  </script>
</body>
</html>